Stavros Dimas, Europe's Mr Environment, has been to London bearing new and shocking health statistics to share with transport activists, the mayor of London and the government. By 2020, if nothing is done, says the EU commissioner, some 300,000 people - the equivalent of a city larger than Newcastle upon Tyne - will die prematurely each year across the 25 European commission countries because of air pollution alone.

Many of the deaths, he says, will come from fine particulates emitted from cars, and the total cost to health services may be anything up to £400bn a year -about six times the cost of running the NHS.

The economics of air pollution, climate change, chemicals, biodiversity, waste and everything else that comes under his huge brief, are close to Dimas's heart. As a former lawyer, World Bank man, Wall Street broker and Greek economics minister, his background has been mostly money - something that got him off to a bad start with green groups and parliamentarians in Brussels when he was appointed last year by the EC president, José Manuel Barroso. His selection hearing was fiery. The greens and the left accused Dimas of incompetence; the socialists were sceptical that he had the experience; and MEPs said his appointment signalled a decreased commitment to environmental issues. Only industry supported him.

But as the Barroso presidency pursues its focused agenda of growth, competition and jobs, there is increased understanding in the corridors of Brussels that the most important role of the environment commissioner these days may be to make the most powerful economic case possible for the environment. They now accept that Dimas's 30-year political and economic experience is useful, and that events such as the huge rise of oil prices and the droughts and floods in Europe strengthen his hand to move Europe towards alternative power such as biofuels.

Dimas admits that environment issues have been under serious attack from senior people in the commission. "We need support because there are people and interests who consider the environment to be second place," he says. "There is always the thinking in Europe that economic growth should be pursued at any cost and that the environment is hindering growth, that economic development should come first."

He won't say who these people and interests are, but rules out the trade directorate, big business and new European countries. "No," he says. "In many instances, big corporations are very environmentally oriented, and the new countries are concerned because of the problems they had [with the environment] in the past - especially with health. In some respects, these countries are better than the older ones. The commissioners, too, are all on the side of the environment." Then he adds: "But no one will admit they are putting the environment second."

It is no secret, though, that hardline neo-liberals in the competition and industry directorates, who pay lip service to the environment but treat it as a burden, have been trying to undermine Dimas and ditch further legislation. Though they have eased off recently, he expects attacks throughout the rest of the presidency.

His arguments against them are powerful. "The eco industries now employ more people than pharmaceuticals or cars, and are growing at 5% a year," he says. "It's natural, when you have so many people unemployed, to look to economic growth, but that doesn't mean you have to sacrifice the environment. Rather, it can contribute to growth and jobs. I say look at China, where economic growth is at the expense of the environment. Tomorrow, they will pay for it."

Dimas is picking up the brief fast. "All this recent extreme weather - droughts in Spain and Portugal, Hurricane Katrina, the floods in eastern Europe - are, I would say, according to the projections and warnings science has given us. It's not possible to link [them] directly with climate change, but the frequency and intensity of these events are worrying."

He is sure Europe has it right and the US has it wrong on global warming. Dimas led the EU in its tough line on climate change during the first weeks of the new commission. At the UN talks in Buenos Aires in December 2004, he tried to negotiate a new system of mandatory emissions reductions to follow the Kyoto targets in 2012 but was shot down by the US.

"We have very different approaches to climate change," he says. "Theirs is based on research and development of new technology. We say [these are] important, but we consider regulation important. The US has ended up with a 15% increase of CO2 emissions on 1990 levels and we have a 9% reduction. That is the difference.

"The EU is leading the world on the environment. It shows in better health for its citizens. America knows what the scenarios are saying. If action is not taken quickly, we will all face great problems."

Dimas says he'll be strong at November's global warming talks in Montreal and is already working with the Chinese and Canadians. "It's going well," he says. "We hope [the US] will be persuaded to move faster."

Meanwhile, he seems impatient with air quality standards. "We need cars to emit much less," he says. "We'll see if the voluntary approach [with industry] works. If not, we may have to legislate."